Well, I guess I opened the ball on the Eemian. For years I have been collecting and reading enormous numbers of papers, books etc. on Quaternary geology and climate change. In the last year, I have really been concentrating on MIS-11 through MIS-1 (today). The period from the T2 (termination 2) through the Holocene, which encompasses the Eemian, has been my focus for the last two years, and involves about 300 papers.
We should probably start another thread for just the Eemian or T2 through MIS-1 to really catch all of the relevant material dating from the penultimate glacial through the Holocene.
However, just on the Eemian, many will probably find this paper by Rohling et al to be quite enlightening:
www.noc.soton.ac.uk/soes/staff/ejr/Rohling-papers/2007-Rohling%20et%20al%20MIS5e%20sea%20level%20rates%20NatGeosc.pdfThis study focuses on proxy and stratigraphic data from the Red Sea region. In many other studies I have by Rohling etc., he and coworkers focus on other areas, particularly areas where stable platforms allow preservation of better sea level highstands/terraces and proxy data.
Interestingly, the 4-6 meter highstand quoted for the Eemian is really more of a general highstand. Many more focused studies find evidence of short-lived excursions to as much as 20 meters above present, as will be clear when you read the paper above. The Grand Caymans, the Bahamas, and parts of the middle east have preserved evidence of this excursion.
Now, MIS-5e, or the Eemian, is not a direct corollary with the orbital dynamics of the Holocene. If you do a lot of reading on the post Mid Pleistocene Transition (MPT), or the period from ~800,000 years ago 800kya) to the present, the orbital dynamics of MIS-11 more closely match the present orbital dynamics. Eccentricity then, as now, is close to the minimum as we are at the midpoint in the 400kya eccentricity maxima that happen every 4th 100kya cycle.
Many workers who have studied MIS-11 find proxy data to suggest that this interglacial may have "skipped a precessional beat" and lasted close to 30k years. There are a few papers out there that suggest that the Holocene will last closer to 50ky or 100ky. These are, of course, predictions, and I have a hard time distinguishing between a rumor and a prediction, the difference being semantic in my perspective.
From the massive amount of proxy research that I have done suggests that no Pleistocene or Pliocene interglacial ever lasted longer than MIS-11 may have, so predictions of 50ky or 100ky do not seem to have a correlative in the past 5 million years of climate proxy data. That does not mean it can't happen, only that it may be a first, should this actually occur.
What we do know from the many Greenland and Antarctic ice core projects, is that temperature has always led GHG increases, with the only exceptions being where the temperatures have abruptly shifted faster than the ocean/atmosphere coupling can come into equilibrium. The temperature excursions happen with stunning speed, often taking only from a few years to just a few decades.
On the major transitions back to the MPT, temperature rise leads GHG changes by 800-1,300 years, and on the drops back to glacial conditions, temperature drops lead GHG changes by as much as several thousand years.
Perhaps the most stunning examples of natural, abrupt, reliable and seemingly unavoidable climate change are the 24 Dansgaard-Oeschger oscillations blatantly obvious, and first found, in the Greenland cores.
It is here where I have two of my biggest problems with AGW prognostications. The first problem concerns the speed, regularity and scale of the natural global warmings. The average cyclicity of the D-O events is the oft-quoted 1,470 cycle, often stated as the 1,500 year cycle. This just happens to match the same length cycle of one of the stronger solar cycles. The range is 1,000 to 4,000 years. The warmings are always very abrupt, occurring, as stated above in from just a few years to mere decades. The range of the warmings averages 8C to 10C with excursions to 16C in some parts of the planet. This means that these events average between one third to one half of the temperature shifts of the major ice age/interglacial cycles! Which tend to range over about 20C. Now with these events averaging 1/3 to 1/2 of the major transitions, which average ~400 feet change in global sea levels, one just has to wonder what this means for rapid sea level excursions in terms of speed and magnitude..... More on that later for those that are interested.
As stated in another post here, a quite interesting study by Sole et al (Physics Letters A 366 [2007] 184–189) which identified three classes of D-O events, A, B and C. The article can be purchased from Science Direct so I will not paste it as it is not in the public domain, yet. Interestingly, all three classes of cycles are in no way triggered by either orbital changes or GHG excursions, particularly the A class, which rapidly relax back to the glacial stage. The B and C classes do indeed indicate a signature related to atmospheric GHG excusrions, but of the opposite sign to that expected. The abrupt temperature rises of all 3 classes happen independently of GHGs, but the B and C classes evince a much slower relaxation to glacial conditions during the last half of the D-O oscillations, essentially easing the transition back to glacial cold.
This has enormous implications. First, as is easily ferreted out from all of the ice core data, GHGs, like the various iterations of the genus Homo over at least the past 2.8 million years, have been spectators to these extraordinary events, not the agent provocateurs. Secondly, if GHGs ameliorate the shifts back into glacial conditions long after the natural temperature rise causation has relaxed (one may suggest the sun here), then if the Holocene, at precisely one half of a precessional cycle long at present (the average age of at least 5 of the past 6 interglacials, excluding MIS-11, dating back to the MPT) is near the end of its duration, what effect will anthropogenic emissions of CO2 likely have?
And here we must both cast further back and guess forward, for not one crystal ball prognostication can be verified at this time, for there is no time machine to take us to the predicted conditions and times.
The ice core data from Antarctica takes us back to about the MPT, give or take one eccentricity cycle or so. Beyond that we must rely upon other proxy data, such as the deep ocean drilling programs and their thousands of sediment cores. Here we find no evidence of interglacials lasting as long as MIS-11 may have, but we do find the enigmatic signature of the 400 kya eccentricity maxima.
And this brings us face to face with our Homo brethren.
"An examination of the fossil record indicates
that the key junctures in hominin evolution reported nowadays at
2.6, 1.8 and 1 Ma coincide with 400 kyr eccentricity maxima, which
suggests that periods with enhanced speciation and extinction
events coincided with periods of maximum climate variability on
high moisture levels."
state Trauth, Larrosoana and Mudelsee in Quaternary Science Reviews 28 (2009) 399–411, another paper you will have to plunk down on, as I have ($32 for those willing to put their wampum where their climate change mouth's are).
Given the single variable rigidity of Hansen, Gore, Schmidt, Monbiot, Tamino, Socold, Steve, glc et al, I find myself wishing that instead of being at the eccentricity minima, we were at one of the 400ky eccentricity maxima. Because what we could really use right now is a sorely needed species shift to the next iteration of the genus Homo, perhaps one more capable of multivariate processing as opposed to single-variable closed-mindedness, one demonstrably and perhaps stupefyingly incapable of producing massive climate change from the factual base of real, not virtual reality based, known climate change events.